(1) Field of the Invention
This invention relates to water flood oil wells and more particularly to introducing a material to chemically interact with metallic ions in water in the formation to produce a plugging precipitate in situ.
(2) Description of the Prior Art
Water flooding in oil field production is a well known process.
When a producing oil well is first drilled, generally, there will be sufficient excess of petroleum to flow into the well where it can be brought to the surface by existing pressure within the well or by pumps. After a certain length of production, the petroleum no longer flows into the producing well. Additional oil can be produced from the zone by water flood process.
Basically the water flood process is: water is injected into the zone in one well and then the water pushes the oil through the zone to another well from which the oil is pumped to the surface.
During this process, channelization may occur. The water, instead of flooding the entire formation, may form channels through the zone and go almost directly from the injection well to the producing well so mostly water is pumped from the producing well instead of oil. In such case, small amounts of oil are produced and excess expense is incurred in pumping excess water.
Many oil bearing formations include connate water, which is that water which is born with the formation or water which originated with the formation. In most instances, connate water is derived from sea water held in the interstices of sedimentary deposits and sealed therein. This connate water has metallic ions therein which would normally include magnesium ions and calcium ions. This would sometimes be expressed: the water has soluble calcium and magnesium salts of chlorides, sulfates, and bicarbonates.
Previous workers in the field have sought to form precipitates within underground formations by injecting a sodium hydroxide solution and then injecting a spacer slug of water and finally injecting a second material such as ferric chloride. Others have used aluminum salts to precipitate aluminum hydroxide when using a hydroxide.
According to the best of my knowledge, no previous worker has depended upon the reaction with the connate water.
The following U.S. Pat. Nos. were considered in preparing this application:
Loomis 2,042,011, Dunn 2,156,220, Kennedy 2,272,672, Chamberlain 2,238,930, King 2,807,324, King 2,747,670, Ramos et al 2,837,163, Bernard et al 3,185,214, Eaton 3,396,790, King et al 3,342,262, Bernard 3,530,937.